Nighttime aeration mode enhanced the microalgae-bacteria symbiosis (ABS) system stability and pollutants removal efficiencies

Utilizing external aeration to enhance the performance of microalgae-bacteria symbiosis (ABS) system has been extensively studied. However, inappropriate aeration damaged ABS system stability. A nighttime aeration mode (NA-ABS) in different aeration intensities (20, 50, 100 mL/min) was adopted to compare to continuous aeration microalgae-bacteria symbiosis (CA-ABS) mode and no-aerated mode on pollutants removal efficiencies and system stability. Results showed that NA-ABS system performed better on total organic carbon (TOC), NH₄⁺-N, total nitrogen (TN) and PO₄^3- removal than CA-ABS system, especially under the aeration intensity of 20 mL/min (NAI20), with the removal efficiencies of 96.59%, 99.18%, 90.30% and 89.16%, respectively. These results were because NA-ABS system prevented CO₂ stripping and provided more dissolved inorganic carbon (DIC) for the microalgae growth. Furthermore, less CO₂ stripping released the competition between microalgae and autotrophic bacteria for the DIC, leading to a more stable ABS system during long-term operation. This paper suggested that NA-ABS system would provide some new insights into ABS system and be helpful for further study.